Embodiments generally relate to efficient optical coupling of Si waveguides on SOI based Planar Lightwave Circuits (PLC) to optical fibers for external transmission.
Efficient optical coupling to and from on-chip photonic single mode (SM) waveguides to an external fiber may be difficult due to the mismatch in size between the SM waveguide and the fiber. For example, the dimension of a typical Silica fiber is approximately forty times larger than a Si channel waveguide. Because of this size mismatch, if the SM waveguide and the fiber are directly coupled, the respective modes of the waveguide and fiber may not couple efficiently yielding only negligible transmission or resulting in an unacceptable insertion loss, >20 dB. Therefore, there is a need for a mechanism to bring these mode sizes close to each other to effectuate efficient coupling.